The present invention concerns a process for the production of a voluminous, particulate polyvinyl chloride usable as a damping material.
It is conventional to precipitate polymers from a solution thereof, by mixing the polymer solution with a liquid which is a non-solvent with respect to the polymer. In such processes, depending on the respective arrangement, powders or fibers are obtained (see, for example, "Ullmanns Encyklopadie der technischen Chemie" [Ullmann's Encyclopedia of Technical Chemistry] 3rd edition, vol. 7, page 296).
It is also known to introduce a polymer solution in metered amounts into hot, but not boiling water, during which step the solvent is removed by evaporation and the polymer is obtained in an aqueous suspension (European Patent Application No. 11,416, Stauffer Chem. Comp.). Finally, a process is also known wherein the polymer solution is dripped onto a moving film of a nonsolvent, and the solvent is evaporated at temperatures of, preferably, 70.degree.-85.degree. C. (U.S. Pat. No. 4,166,171, Goodyear Tire and Rubber Comp.). This process preferably involves the processing of polyvinyl chloride solutions in tetrahydrofuran by adding these solutions to an aqueous salt or glycerol solution.
However, the aforementioned methods all exhibit significant disadvantages. At the aforementioned temperatures of about 70.degree.-95.degree. C. for the nonsolvent, the evaporation of the polymer solution takes place relatively slowly, so that a tacky intermediate stage occurs. This leads to caking of the precipitated polymer material and to deposits on the agitator. In addition, the increase in volume of the thus-precipitated polyvinyl chloride is relatively low.